Grip Roll

[Skye]

Can anyone offer any additional advice on how to reduce grip roll on high traction surfaces? I am currently driving a B44.1 and am suffering from a lot of grip roll.....

As a newcomer to the game I have raced three times outdoors, once at Stotfold, once at Hinckley and once at Silverstone. So twice on astro and once on grass.

The first time was at Stotfold and simply cutting off the two outside rows of spikes on the fronts pretty much cured the problem there so the grip must be a bit lower than the other two.

Then I went to Hinckley and found that it was still grip rolling every time. I then proceded to cut of a row of spikes off of the outside and inside of the rears as well as the inside row on the fronts. I was then advised to change the springs to blues (front) and silvers (rear) to stiffen it up a bit, and also to add some weight. I added 60g of stick on weights to the central battery stay beneath the driveshaft and this again seemed to help. It didnt eliminate it but it raised the breaking point so I could go a little faster before it rolled.

I then raced at Silverstone on Tuesday and the problem was there in abundance again. Everybody was saying how much grip there was so I wasnt alone, but when I observed the other 4wd cars they seemed a lot more planted.

I know that I am not as good as the more experienced guys, so that will make a difference. But even allowing for that, I was still grip rolling on less technical areas such as the sweeping bends into and out of the straight where the other cars were hammering it through these bends significantly quicker than I could before I was losing it and grip rolling.

So Im scratching my head a little now. There has been massive improvement from where I started, of that there is no doubt. But its still not quite there in terms of keeping it planted and reducing the grip roll as much as is physically possible.

So my set up is :
FRONT
20mm ride height
Blue Springs
40wt oil
Worn yellow minispikes (2 outer rows cut off, 1 inner row cut off)
2 x 5g weight added (one either side of servo)

REAR
20mm ride height
Silver Springs
30wt oil
Worn yellow minispikes (1 inner and 1 outer row cut off)
60g weight added under rear driveshaft

All of the other settings are untouched since I built the car to the kit manual instructions.

I know this is something that cant be eliminated completely but having watched the other 4wd cars closely on Tuesday night I did observe that they were able to carry much much more speed into a bend without it rolling. At the moment I feel like I am driving on the edge as several times tuesday night I had it on two wheels round a bend, and many more times it broke free and ended up on its roof.

If anyone has had similar experiences and managed to cure it, or if you drive the same car and manage to keep it glued to the track then any advice would be much appreciated!

Many Thanks!

[/tobys]

Limiting droop can help cure grip roll but at the expense of bump handling. Try adding 1-2 1mm spacers underneath the piston and see if that improves matters.

Also, try a front roll bar if you've got one.

HTH

[Skye]

Originally Posted by /tobys

Limiting droop can help cure grip roll but at the expense of bump handling. Try adding 1-2 1mm spacers underneath the piston and see if that improves matters.

Can you explain how you mean please? A couple of months ago I knew zero on setting up a car so am having to learn fast, but dont know quite what you mean by this? Thanks!

[/tobys]

If you picture the shock shaft and the piston running inside the shock body, you would put some spacers on the shaft under the piston (below the E clip) and inside the body so that you are limiting down travel. This helps limit roll at the expense of bump handling (as you don't have as much downtravel/droop).

[sosidge]

Originally Posted by Skye

Can you explain how you mean please? A couple of months ago I knew zero on setting up a car so am having to learn fast, but dont know quite what you mean by this? Thanks!

If I can answer on his behalf, you open up the shocks and put the spacers on the shaft under the piston, this will limit the downtravel. AE sell packs of 30thou spacers for that purpose.

Personally speaing, from looking at your setup I wonder whether you are running the car too low. The geometry is designed around a certain ride height (more like 23/24mm), and by dropping it down low you are making the roll centre quite a bit lower which increases the likelihood of grip roll, you are also more likely to bottom the suspension out, which will cause a sudden roll.

You already know about trimming spikes, so aside from that I would suggest decreasing your steering lock a little, and just advise you to try and be as gentle in your steering movements as you can be. Try and keep the car running straight unless you absolutely have to be steering, use the brakes to slow the car down rather than scrubbing the speed off with steering input.

[Skye]

Thanks Guys, some good ideas to try out (not all at once though! )

Sosidge, I was surprised by your comment ride height. I would have thought a lower ride height and lower centre of gravity would have helped reduce the grip roll? You almost certainly know more than me though so I will certainly give it a try!

I am already having to be quite heavy on the brakes as if I try to scrub speed off by sliding it just goes over. When I was watching the other 4wd they were entering the corner at the end of the straight faster and were sliding a little in the corners where my car would just bite and roll if I tried to do that.

[/tobys]

Are you running the kit locations for shocks and camber links?

[F1END]

I had a similar problem first time out at Silverstone and was advised to use softer oil in my shocks (as well as all the spike trimming). I had 45wt in the front and changing to 35wt helped no end.

[dmsykes]

We had the same problems with our B44 & BJ4 cars in the past.

One thing we tried was to remove the inside & outside row of spikes & also use a harder foam in the front, we also nearly always ran rear anti roll & hard front springs.

If in extreme cases Stotfold (astro) we restorted to running (2wd) Slim mini spikes on the front.